So if you were asked to describe the sort of food producer that will matter most in the next 40 years, you would probably say something like this: one that has boosted output a lot and looks capable of continuing to do so; one with land and water in reserve; one able to sustain a large cattle herd (it does not necessarily have to be efficient, but capable of improvement); one that is productive without massive state subsidies; and maybe one with lots of savannah, since the biggest single agricultural failure in the world during past decades has been tropical Africa, and anything that might help Africans grow more food would be especially valuable. In other words, you would describe Brazil.

The briefing also derides “inefficient hobby farms” as a purported alternative to Brazil’s “productive giant operations.”

While there are definitely economies of scale in agriculture, this analysis leaves out the crucial issue of fossil fuels. Within the next few decades, it must be hoped that humanity begins a serious process of moving beyond fossil fuels, in order to reduce the harmfulness of climate change. Even if we are not so enlightened, it is possible that peak oil will massive increase prices and reduce supply.

When planning out how the world will feed itself during the decades ahead, a key consideration must be how we will do so without the cheap liquid fuels that power our industrialized global food system.

SIR – Your briefing paints a cheery picture of the potential for Brazil to meet the world’s growing food needs (“The miracle of the cerrado”, August 28th). However, two important facts should temper our optimism about this remarkable agricultural story.

First, Brazilian climate change law requires steep reductions in greenhouse gas emissions by the year 2020: 36-39% below 2005 levels. The government plans to achieve this through an 80% reduction in deforestation in the Amazon region and a 40% reduction in deforestation of the cerrado savannah. It is on track to reach the Amazon goal, but will only succeed in curbing the 7,000-20,000 plus square kilometres of annual clearing in the cerrado if most agricultural expansion moves onto unproductive cattle pastures. An even greater challenge for Brazil and a world facing a dangerous climatic disruption will be to diminish agriculture’s dependence on fossil fuels and noxious chemicals.

Second, you perpetuate the view of the cerrado as the expendable, scrubby neighbour of the far more glamorous Amazon rainforest. In fact, it has more plant and animal species than any other savannah in the world and is more threatened than the rainforest—at least in the coming decade. The world is moving rapidly into a food crisis and there are no free lunches.